Calcium isotopic patterns in enamel reflect different nursing behaviors among South African early hominins.

Abstract

Nursing is pivotal in the social and biological evolution of hominins, but to date, early-life behavior among hominin lineages is a matter of debate. The calcium isotopic compositions (δ^44/42Ca) of tooth enamel can provide dietary information on this period. Here, we measure the δ^44/42Ca values in spatially located microsized regions in tooth enamel of 37 South African hominins to reconstruct early-life dietary-specific variability in <i>Australopithecus africanus</i>, <i>Paranthropus robustus</i>, and early <i>Homo.</i> Very low δ^44/42Ca values (<-1.4‰), indicative of milk consumption, are measured in early <i>Homo</i> but not in <i>A. africanus</i> and <i>P. robustus</i>. In these latter taxa, transitional or adult nonmilk foods must have been provided in substantial quantities relative to breast milk rapidly after birth. The results suggest that early <i>Homo</i> have continued a predominantly breast milk-based nursing period for longer than <i>A. africanus</i> and <i>P. robustus</i> and have consequently more prolonged interbirth interval.